Prostate specific antigen (PSA) is a common blood test used by doctors to assess whether an individual has prostate cancer. It also predicts the risk of developing prostate cancer sometime in the future. It’s a good blood test but not a perfect one and the risk of cancer does increase with increasing levels of PSA in the blood tested.
Doctors have improved the accuracy of the test by also looking at the rate the PSA rises every year, by modifying the interpretation of the results in accordance with the age of the patient, and measuring additional modifications of PSA.
The test is usually performed in conjunction with a digital rectal examination, and if the doctor feels the risk of cancer is sufficiently high, a recommendation may be made to visit a specialist urologist and to consider a prostate biopsy, which is the only way cancer can be formally diagnosed.